<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>伪类/伪元素</title>
    <style>
        .pseudo-ele::before{
             content: 'before ';
        }
        .pseudo-ele::before{
            height: 0;
            /*这样字符串拼接*/
            content: attr(title) ' before ';
            /*display: table-cell;*/
        }
    </style>
</head>
<body>
    <div class="pseudo-ele" title="title">me</div>
</body>
</html>